Add dynamic-programming module: ten classic DP problems, memoization vs tabulation vs space-optimised, call-count and pitfall transcripts (11 tests)

2026-11-09 08:41:01 +00:00
parent 911aef5515
commit cb1b28682f
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+Fibonacci: three things that go wrong
+=====================================
+
+1) HashMap.computeIfAbsent as the memo, recursive mapping function, n = 10
+   -> java.util.ConcurrentModificationException
+   same idea written as get / compute / put -> 55
+
+2) The answer outgrows a long
+   fib(92) = 7540113804746346429
+   fib(93) -> ArithmeticException: long overflow   (Math.addExact refuses to wrap around)
+   plain + instead of addExact would silently return -6246583658587674878
+
+3) Recursion depth, House Robber with every house worth 1, in a thread with a 256 KB stack
+   memo       n =    500 -> 250
+   memo       n = 50,000 -> java.lang.StackOverflowError
+   tabulation n = 50,000 -> 25000